The Boston Marathon is tomorrow, one of the marquee events for distance runners around the world. As with many sports, it used to be a men's-only event until 50 years ago, when Kathrine Switzer became the first woman to wear a Boston bib number and race. Now she's prepping to run it again at the age of 70. Kathrine Switzer joins me now from Boston. Welcome.

KATHRINE SWITZER: Thank you very much. It's wonderful to be with you.

GARCIA-NAVARRO: So it's hard to imagine these days that women would be banned from running in a marathon. Take us back to 1967. What was the thinking behind that?

SWITZER: In 1967, when I pinned on that bib number, I really wasn't trying to prove anything because a woman had actually run the Boston Marathon the year before by just jumping out of the bushes and running. There was nothing about gender in the rulebook in those days because everybody assumed a woman really couldn't run and didn't want to run, and why even bother with it in the rulebook or on the entry form?

And in sports, the longest distance in the Olympic Games, in fact, was just 800 meters. It was feared that anything longer was going to injure women, that they wouldn't be able to have children or they somehow turned into men. That was what was the theory.

GARCIA-NAVARRO: Really, that they were going to turn into men or that their uterus would be damaged?

SWITZER: Absolutely. You know, it was amazing. You'll never be - ever have children, they said. You're going to get big legs. You're going to grow hair on your chest. It was hilarious, the myths. And, of course, when people hear myths, they believe them because to try otherwise might mean damaging yourself. So people were afraid and they just went about their lives that way and restricted themselves.

GARCIA-NAVARRO: But you didn't. You actually entered that 1967 marathon. Tell us a little bit about how you did that and what - and the story behind that.

SWITZER: Well, I entered the race simply because my coach had been a 15-time Boston Marathon runner. And he didn't believe a woman could do it, but he loved running with me and telling me stories about the Boston Marathon. So he energized me. And, you know, when I told him that I really wanted to try and he said he didn't believe a woman could do it, I was bound and determined to prove him wrong.

So we did the - all the right things. We followed all the rules. We signed up using the correct entry form and had our travel permits and our AAU cards. We were parts of the federation. The only thing that challenged it was how I signed my name. I sign my name K.V. Switzer, with my initials. And when the entry form went in, they thought it was from a man.

GARCIA-NAVARRO: The race organizers realized there was a woman on the course, of course. How did they find out, and what happened when they did?

SWITZER: At about a mile and a half into the race, the press truck went by us, and they saw that I was a woman in the race wearing numbers and they began taking pictures. And alongside of the photographer's truck came the officials' press truck. And the race director was on the truck and the guys were teasing him. And he got so angry that there was a girl in the race that he stopped the bus and jumped off it and ran after me and attacked me in the race and tried to pull off my bib numbers, screaming at me, get the hell out of my race and give me those numbers.

And I was just blindsided by this. I was terrified. I was scared. And my boyfriend came along with a full streak and gave the official a cross-body block and sent him out of the race instead. You know, we laugh about it now because it's so funny when a girl is saved by her burly boyfriend. But, you know, I said to my coach immediately after the incident - and I said, I have to finish this race now because if I drop out of this race, nobody's going to believe that women are serious.

GARCIA-NAVARRO: We should tell our listeners you won the New York City Marathon in the '70s. You came in second in Boston once. You've been running ever since. And now, again, you are going to run the Boston Marathon at 70 years old. What's - what are your hopes for the race day?

SWITZER: You know, what's going to happen on Monday, Patriots' Day here in Boston, is to come back 50 years and celebrate the fact, first of all, that I can run, that I'm capable of doing it, amazingly enough, and I'm very, very grateful for that. And I'm also very grateful for the opportunity to thank a city and the streets that changed my life and help to empower millions of women all around the world and change the face of the sport.

GARCIA-NAVARRO: Kathrine Switzer, good luck out there tomorrow and what an honor to speak with you.